Recent years have seen increasing concern about the effects of the discharge of chloro fluoro carbons (CFCs) and related compounds such as hydro fluoro carbons (HFCs) and hydro chloro fluoro carbons (HCFCs) into the atmosphere. Scientists have determined that CFCs and, to a lesser extent, HCFCs break down the ozone layer at the perimeter of the earth's atmosphere. The ozone layer in turn has long provided a screening effect for screening out ultraviolet light emanating principally from the sun.
It is feared that continued break down of the ozone layer will result in increasing amounts of ultraviolet energy reaching the earth's surface rather than being screened from the surface by the ozone layer and that the increase in ultraviolet light striking the surface will cause an increased incidence of various types of skin cancers. Consequently, every use of CFCs is in the process of being re-evaluated to determine suitable alternates that will not cause break down of the ozone layer. For example, CFCs have long been used as propellants in aerosol containers. Their use in such containers has been substantially halted in recent years in favor of other compounds.
CFCs and HCFCs have also been widely used as refrigerants in refrigeration systems of all sorts. And, of course, when these refrigerants escape the closed loops found in such refrigeration systems, they pose the same danger to the ozone layer as propellants released from aerosol containers. And while, as alluded to previously, HCFCs do not have as deleterious effect on the ozone layer as CFCs, they do promote atmospheric changes that may result in global warming, that is, the so-called greenhouse effect. Similarly, HFCs, which have also been used in refrigeration systems as refrigerants tend to promote global warming when released into the atmosphere, although they do not noticeably contribute to the destruction of the ozone layer. Other compounds that have the ability to serve as refrigerants as, for example, hydrocarbons (HCs) of low molecular weight do not pose dangers to the ozone layer or raise the potential for global warming. However, they are highly combustible such that release to the atmosphere in areas of potential fire or explosion danger cannot be tolerated.
While many refrigeration systems are not at all prone to leak refrigerants to the atmosphere or ambient, those used in connection with vehicles are relatively leak prone. During operation of the vehicle, the refrigeration system, whether used for cooling cargo or whether utilized for cooling a passenger compartment, or both is subject to substantial vibration as the vehicle traverses the underlying terrain. Since fittings are required to connect the various components to one another, the possibility of leakage through such fittings as a result of vibration during operation of the vehicle is substantial.
Moreover, since the compressors in vehicular refrigeration systems, particularly air-conditioning systems, are typically engine driven, they are mounted rigidly to the engine and will move with the engine as the same shifts on its mounts as a result of various torque requirements and changes in loading as well as engine speed and acceleration or deceleration conditions. At the same time, the condenser and the evaporator in such systems are fixed to the vehicle frame and thus do not move with the engine as it shifts on its mounts.
Relative movement between the compressor on the one hand and the condenser and evaporator on the other is thus taken up in conduits and interconnecting fittings; and this relative movement in turn is also prone to cause leakage over a period of time.
Finally, the seals used in such systems frequently employ elastomers in order to accommodate vibration and relative movement between system components. Over a period of time, such seals may tend to shrink if not subjected to the refrigerant and/or lubricant within the refrigerant at periodic intervals. Thus, automobile manufacturers frequently suggest that air conditioning systems be cycled for several minutes at least once a month even during the winter months to prevent loss of the refrigerant charge. If, however, the operator of the vehicle does not attend to such cycling, ultimately discharge of part or all of the refrigerant charge may occur through shrunken seals and where the refrigerant charge is the CFC R12, which is highly destructive of the ozone and which is the most commonly used refrigerant in automotive refrigeration systems, the problem is exacerbated.
The present invention is directed to minimizing the effects of undesirable leakage of refrigerants to the atmosphere. In particular, it is directed to minimizing the effects of leakage of CFCs, HCFCs and HFCs to the atmosphere when the same are used as refrigerants and is also directed to providing a refrigerant utilizing system that may advantageously employ HCs without generating a potential fire or explosion hazard to persons benefiting from the refrigeration system.